A Bimetallic Nanozyme Synergistic Effect-Driven Enzyme Cascade Nanoreactor for Instant Immunoassay

This study presents a colorimetric sensor for cancer screening utilizing the bifunctional enzyme activity of NiCo Prussian blue analogue (PBA), a PBA material. By introducing oxygen vacancies and employing a dual-metal doping strategy, NiCo PBA overcomes the limitations in catalytic activity observed in single-metal-doped materials (such as Ni PBA and Co PBA), significantly enhancing both peroxidase-like (POD) and catalase-like (CAT) activities. Compared to single-metal-doped Ni PBA and Co PBA, NiCo PBA exhibited a 30.08-fold increase in POD activity and a 4.83-fold increase in CAT activity, demonstrating higher sensitivity in carcinoembryonic antigen (CEA) detection. By integrating NiCo PBA with a cascade catalytic reaction principle, we developed a highly efficient and sensitive CEA detection method. NiCo PBA was utilized as a catalytic material in this method. Under the action of glucose oxidase, the decomposition of hydrogen peroxide was catalyzed by NiCo PBA, and oxygen was generated. Furthermore, a blue flocculent substance was produced when NiCo PBA was reacted with a chromogenic substrate. Through mutual verification by these two methods, the quantitative determination of CEA in serum samples was achieved. The experimental results demonstrated that the POD-like activity detection range was 0.2-50 ng mL^-1, with a limit of detection (LOD) of 0.061 ng mL^-1, while the CAT-like activity detection range was 0.1-20 ng mL^-1, with an LOD of 0.028 ng mL^-1. The sensitivity of this method was substantially increased compared to monometallic materials. Furthermore, this strategy possesses good scalability and can be adapted for the detection of various analytes by replacing different recognition units, providing an efficient detection platform for early cancer screening.